UPGR_PH100_Study.pdf

Upper Peninsula Geological

Repository Ventilation Study

December 2023

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Table of Contents

Background/Existing Conditions

Analysis/Options

Recommendations

Appendix A - Photographs

Appendix B – Sketch of Proposed Recommendation

Appendix C –Cut Sheets of Proposed Equipment

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The Upper Peninsula Geological Repository operated by Michigan Environment, Great Lakes and Energy (EGLE) is housed at a former receiving warehouse on the decommissioned K.I. Sawyer Air Force base in Gwinn, Michigan.

Background/Existing Conditions

The facility stores geological core samples from throughout Michigan’s Upper Peninsula. The building consists of two separate areas, an office space and sample storage space. The owner has indicated that Radon has been measured within the spaces due to off gassing of samples in the storage space. During the owner's

Radon testing they observed that when the doors where opened and fresh air entered the space the Radon levels decreased. By addressing ventilation concerns regarding code requirements, building moisture, and propane fork truck use, there is an expected result to lower radon levels. The purpose of this study is to review the ventilation within the spaces and provide recommendations to meet the minimum ventilation requirements of the Michigan Mechanical Code, OSHA requirements for propane fork truck use, and to minimize migration of air from the storage area to the office area.

A team of OHM Advisors professionals toured the site on October 25, 2023 to further understand the usage and the building as a whole.

The office facility is heated via a gas fired hot water boiler with perimeter radiation. Ventilation to the office area is achieved by two small, fixed core energy recovery units. Each unit is approximately 180 cfm (see

Figure 1) and has no supplemental heating. There is an abandoned ventilation/heating/cooling unit on the roof that previously served the electrical room at the north end of the office area but is no longer operational.

A number of the office spaces have split system cooling units with a central condensing unit rejecting heat into the storage area.

The storage area is heated by a number of gas-fired unit heaters (see figure 3). Many of the heaters are currently inoperative. There is no ventilation in the storage area.

The storage area of about 40,000 square feet had no ventilation air. The desired indoor conditions for the storage area is 60 degrees Fahrenheit during the winter and no summer cooling.

No noticeable pressure differential was noted between the office and storage area at the time of our visit.

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Analysis/Options

The industry recommended method to mitigate Radon is by source capture which in a building like this would be difficult.

Based on the 2015 Michigan Mechanical Code (MMC) the office area requires just over 500 cfm of ventilation air.

Typically, where office spaces directly interact with areas of other usage it is recommended to hold the office at a slight positive pressure to the adjoining space to assist in limiting the migration of contaminants into the office. This pressure differential is typically 0.05 in water column (WC). Currently the doors between the office and storage area have visible leakage areas (see figure 2). It is recommended that jamb seals and door thresholds and sweeps, be added to all the doors to reduce the area for air leakage. We also recommend the installation of door closers to keep doors from being unintentionally left open.

The storage area can be accessed from the office by three (3) single doors and a single double door. There are also two doors to the exterior from the office. One of the doors to the exterior has a vestibule and will not be included in this calculation. Once jamb seals are installed the only area for leakage will be limited to a small area at the bottom and between the double doors. This calculates to 28 lineal feet of leakage. Using a 1/16” gap we arrive at 1.3 square feet, rounding up to account for minor window leakage we conclude an approximate leakage area of 1.5 square feet.

The storage space that houses the specimens also has the use of a propane fired fork truck for the movement of sample boxes/pallets.

Based on the Michigan Mechanical Code (MMC) the storage area requires 0.12 cfm/square foot of ventilation air or about 4,700 cfm. Based on Occupational Safety and Health Administration (OSHA) recommendations there shall be 5000 cfm of ventilation air for a well-tuned operating propane fork truck. The 5000 cfm is the minimum required for the space working out to an air change rate of 0.5 air changes per hour (ACH) or one complete air exchange in 2 hours when used as continuous ventilation.

One option to eliminate the combustion contaminates from the fork truck operation is to utilize an electric model fork truck opposed to the current propane fired unit.

The final design could include the flexibility to operate the storage area ventilation only when the area is occupied, some period of time prior to occupancy, or continuously. The system could also be designed to allow for varying flow rates, one flow rate for general occupied times, a higher flow rate when the fork truck is operating, and a third/lower flow rate during unoccupied hours to provide minimal ventilation.

In facilities that monitor combustion contaminants such as enclosed truck parking facilities there is typically no continuous ventilation and an airflow rate of 4 ACH as intermittent ventilation to purge contaminants.

Based on the volume of this storage area the flow rate to achieve this 4 ACH would equal 42,000 cfm.

It is recommended that the facility utilize a continuous ventilation strategy to reduce the accumulation of unwanted pollutants at a flow rate between the minimum of 5000 cfm and the intermittent rate of 42,000 cfm. As seen below in table 1, the operational cost of continuous ventilation is significant.

We reviewed if it is allowable to introduce un-tempered air into the space (and exhaust an equal amount) in lieu of providing an indirect heating unit. This method can cause operational trouble due to extremely cold air entering the space and our review of the MMC found that this is not listed as an approved method of

Uppper Penninsula Geological Repository Ventilation Study Page 5 introducing air to the space. During design, contact can occur with the mechanical authority having jurisdiction for discussion to confirm if this method would be approvable.

Another option is the addition of vestibules or “air locks” between the storage area and office by means of two sets of doors back to back with air pressurization between. Based on the number of openings this did not appear to be a construction cost savings over the 5000 cfm ventilation option. Fewer openings would make this more financially viable.

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Recommendations

Storage Area

OHM proposes adding the following equipment to the area. An indirect gas fired make up air unit located outdoors on a grade mounted stand. The unit would be 100% outside air and ducted through the storage area. The air would be removed with an exhaust system to keep a slight negative pressure with respect to the exterior and office area. The exhaust fan/s would be wall mounted for easier serviceability. The exhaust inlet being located across the building from the supply outlets would create a sweeping of the air from location of supply discharge to exhaust removal. The exhaust would pull from both high in the space as well as low to the floor to capture contaminants both lighter and heavier than air. See Appendix B.

Office Area

Based on a leakage area of 1.5 square feet a ventilation differential of 800 cfm would be recommended. In order to allow for proper energy recovery, the manufacturer recommends a 2000 cfm supply unit with 1200 cfm of return/exhaust providing an 800 cfm positive offset in the office area. The air differential means that there would continuously be more supply/ventilation air introduced to the office area than return/exhaust removed. This will create the office area pressure positive with respect to the exterior and storage area. This

ERV should run continuously to maintain the differential.

It would be recommended to install differential monitoring instrumentation with an alarm to alert occupants if the designed pressure balance was malfunctioning.

A unit with a larger air flow and therefore higher air change rate uses proportionally more energy to operate.

Below is a table that identifies the estimated operational costs for a unit per year based on air flow. The operational cost is based on an indoor temperature of 60 degrees F, minimal existing wall and roof insulation and an outdoor weather profile for the local area. A gas rate of $10 per thousand cubic feet (MCF) or $1 per therm and an electric rate of $0.15 per KWh were used in the modeling.

Based on the current gas piping, a meter and regulator replacement would most likely be required as well as a new line to feed the additional equipment.

Table 1 Operating costs of different options in Storage Area

Air flow Annual Operating Cost

5,000 cfm (0.5 ACH) $59,300 10,000 cfm (1 ACH) $101,000 15,000 cfm (1.5 ACH) $145,000 42,000 cfm (4 ACH) $381,000

Table 2 Estimated operation cost @ 24 hr operation

Office Area Annual Operating Cost 800 cfm Pressure offset $15,000

Appendix A - Photographs

Figure 1 Existing Energy Recovery unit

Figure 2 Example of leakage under door

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Figure 3 Gas Fired Unit heater in Storage area

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Appendix B – Sketch of Proposed Recommendation

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Appendix C –Cut Sheets of Proposed Equipment

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